The present invention relates to a heater system for an automotive vehicle, and more particularly relates to a coolant circulation system for a heater of an automotive vehicle, which can provide appropriate circulation of coolant to a heater for a wall of the intake passage of the engine of the vehicle, and also to a heater for the passenger compartment of the vehicle.
In an automotive vehicle such as a passenger car the engine of which is cooled by the circulation of a coolant such as water it is known for hot coolant abstracted from the engine cooling system to be supplied to a heat exchanger for the wall of an intake passage of the engine, in order to heat up this intake passage wall so as to promote the vaporization of droplets of fuel included in the air-fuel mixture which is being sucked into the engine through said intake passage. This function is very helpful for improving the combustion of fuel in the combustion chambers of the engine, and in order to improve fuel efficiency of the engine as well as to improve the quality of the exhaust emissions thereof. This heating of the wall of the intake passage is particularly desirable during cold weather conditions such as winter conditions, in other words when the temperature of the air external to the vehicle is low and also the temperature of said wall of said intake passage when unheated may also be low, because in such cold weather conditions the problems associated with poor vaporization of the fuel are much more severe. On the other hand, in warm weather conditions such as summer conditions, this heating of the wall of the intake passage of the engine needs only to be performed to a lesser amount, because the fuel is much better vaporized in the carburetor or the like of the vehicle due to the higher temperature of the intake air, and also because the intake passage wall may be warmer in any case even when unheated. In the prior art, therefore, a system has been required to be provided for altering the amount of coolant flow to the above mentioned intake passage wall heat exchanger according to the temperature external to the vehicle, such as for example a system including a control valve for regulating the amount of coolant flow supplied to said intake passage heat exchanger. Such a system also requires a thermostatic control valve or the like for sensing the temperature of the ambient air.
Further, it is also per se well known to provide a heat exchanger for heating up the air inside the passenger compartment of the vehicle, both from the point of view of passenger comfort and also in order to provide demisting or defrosting action for a windshield of the vehicle. Again, such a passenger compartment heat exchanger is typically supplied with hot coolant abstracted from the engine cooling system. Such heating action for the air in the passenger compartment is only, typically, required by the driver of the vehicle when the external air temperature is low, i.e. during winter conditions, and is not typically required when the external air temperature is reasonably high as during summer conditions. Accordingly again a system has been required to be provided for altering the amount of coolant flow to the above mentioned passenger compartment heat exchanger according to the desire of the operator, such as for example a system including a control valve for regulating the amount of coolant flow supplied to said passenger compartment heat exchanger. Such a control valve is typically manually controlled by the driver of the vehicle.
Thus, in the prior art, in a vehicle with both these types of heat exchanger, it has been necessary to provide two separate conduit systems for leading hot coolant to these two heat exchangers, and two independent control valves therefor, as well as to provide some form of automatic control for the control valve for controlling the coolant flow to the intake passage heat exchanger; and this has entailed a necessarily complicated system, with consequent decrease in manufacturability and reliability, as well as increased cost. Further, since in the prior art the two heat exchangers have been arranged in parallel with regard to their coolant supply systems, it has been necessary for the pumping power of the coolant pump of the engine of the vehicle to be relatively high, thereby further entailing an additional cost.